It has long been known that the food value of grains fed to animals can be improved through a roasting process in which the grain kernels are heated to a high temperature. The roasting process denatures protein in the grain, rendering the grain more susceptible to digestive enzymes of animals, and also tends to change or partially gelatinize starches in the grains to similarly render the starches more susceptible to digestion. Further, the roasting process ordinarily gives rise to a pleasant aroma, rendering roasted feeds more appetizing to animals. See Roasted Corn vs. High Moisture vs. refrigerated vs. Artificially Dried Whole Shelled Corn, Progress Report, Iowa State University, A.S. Leaflet R133, August 1970.
The roasting process is quite complicated, and involves various chemical and physical reactions in varying degrees of completeness. If a grain product, such as corn, is underroasted, the product will not have the digestability nor the pleasant aroma of a properly roasted product. On the other hand, overroasting can cause charring, can reduce protein useability, and results in a carmelized, charred odor that is repulsive to animals. Reference is made to Perry, T. W., L. M. Hammond, R. C. Peterson and W. M. Beeson, Value of Roasting Corn and of injectable Vitamin E or Selenium for Finishing Heifers, Report of Animal Sciences Department and Lynnwood-Purdue Agricultural Center, Purdue University, 1970.
Various roasters and other heating devices have been proposed. One such device is shown in U.S. Pat. Nos. 3,343,961 and 3,368,475. Another roaster, sold by the applicant, consists of a generally horizontal, rotating drum into which grain or other particulate material is dropped from an auger extending into the drum, and a heater, such as a gas burner, is employed to heat the particles as they fall and are tumbled through rotation of the drum. Although reasonably satisfactory roasting results have been obtained with this device, improvements need to be made to improve the uniformity of the roasting process and to avoid the production of underroasted or overroasted particles and clumps of particles. See also McKenzie, B. A. and J. R. Gottbrath, High Temperature Grain Processing--Procedures and Equipment-, American Society of Agricultural Engineers Paper No. 71-814 presented at the 1971 ASAE Winter Meeting, Chicago, Ill. December, 1971.